After eight long years, Cameron Douglas can finally travel to LA while on probation to visit his 100-year-old grandfather, Hollywood legend Kirk Douglas, it emerged on Wednesday.

Page Six reported that Cameron — son of “Wall Street” star Michael Douglas — missed Kirk’s 100th birthday because he wasn’t allowed to travel on parole after serving nearly seven years on drug charges.

But on Wednesday, a Manhattan federal judge approved his request to make the trip after Cameron, 38, proved he’s remained sober following an embarrassing parole violation in April.

He’ll make the trip in about a week.

A family friend told us: “Without question this is a great relief to the family. They’ve been really eager to have him go and reconnect, so he can have a solid, stable base.”

Sources say Cameron’s penning a tell-all about his Hollywood upbringing, jail time and recovery — and could use reuniting with Kirk as material.

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At Wednesday’s hearing, a probation officer told Judge Richard Berman that the “sweat patches” Douglas has been forced to wear to test for drugs have routinely shown he’s clean since he was caught with marijuana in his system in April. He’s also been in a treatment program that includes a daily chaperone to therapy sessions.

The clean bill of health opened the door for Cameron’s lawyer to request that his client be allowed to travel to see his famous granddad, despite parole restrictions requiring him to remain in the area.

“Every time he speaks with Cameron on the telephone, he asks when he will come visit him,” the lawyer said of Kirk. “They have a very close relationship.”

Cameron thanked the judge profusely, and said outside court that the trip to LA has nothing to do with his grandfather’s health. “He is healthy,” he said.

Cameron was accompanied to court by his Brazilian yoga-instructor girlfriend, Viviane Thibes.

A pal tells us that these days Cameron’s “a homebody . . . He mainly likes to just walk the dog or stay home.”